What i need to do is pretty simple stuff, but i cant work out how to do it without creating extra columns with formulas.

Say i have 2 columns of data, A and B, and i want to subtract the value of A from B, so if to start with A contains the value 10 and B 30, afterwords B would then contain the value 20

I can start a new column C with =B1-A1 but i DONT want a new column with dynamic formula driven data, i just want to alter the data in column B!

This seems like such a simple thing to do, but i cant work it out.

Any help very much appreciated.